1. Field of the Invention
The invention relates to a process for determining the onset of tread rubber separations of a tire on a vehicle.
2. Discussion of Background Information
Ever-increasing demands on the safety of motor vehicles increasingly require a detection of all the parameters influencing and representing the driving and moving condition of a motor vehicle to be as comprehensive as possible for use in intelligent systems for chassis and vehicle control and adjustment. In particular typical dangerous situations, such as those which can occur during the sudden separation of the tread rubber or parts thereof, the danger needs to be reliably identified and appropriate warning or control signals need to be triggered.
The greatest dangers of sudden tire damage are caused by tread separations, since in most cases—particularly when driving at high speeds—the tire bursts within fractions of a second after the tread rubber separations, leading to loss of control of the vehicle and to serious accidents.
In the past, detecting and displaying the onset of tread rubber separations, a moment in which the vehicle can still be brought to a controlled stop, has been a problem in metrological terms, since these conditions are hard to detect. We have hitherto managed by using the display of other parameters which indicate a critical condition of the pneumatic tire, to also detect the onset or occurrence of tread rubber separations.
Since it is known that if internal tire pressure is too low, this will or can lead to critical damage to the pneumatic tire, a number of solutions have already been proposed in which the air pressure in the tire is registered and displayed to the driver when pressure falls below a preset desired value, causing him to stop the vehicle. Such suggestions are known from, e.g., EP 630 769 A1, EP 826 525 A2, EP 787 606 A2 and EP 786 362 A2. Finally, a system for detecting a so-called emergency operation situation is known from DE 199 08 701 A1. This system requires a tire with emergency support bodies, whereby the support body features imbalances that produce frequencies by contact with the inside of the tire in an unpressurized state, which frequencies can be detected as signals of disturbance by a sensor, in particular by a conventional ABS system.
Such solutions utilize the correlation that in many cases exists between insufficient air pressure and the resulting damage to the tire structure, in particular to the tread rubber. However, insufficient air pressure is only one cause of the dangerous tread rubber separations. They can also occur quite irrespective of the internal tire pressure, e.g., by exceeding the maximum allowable speed for the type of tire. If, for example, a snow tire restricted to 160 km/hr is driven at 180 km/hr for approximately 20 minutes, this can lead to tread rubber separations due to overheating, despite the correct air pressure. Other causes that are regularly attributable to driver error can also lead to tread rubber separations despite maintaining the correct air pressure, such as tires that are too old, too worn, or the like. Retreaded tires can also be problematic.
U.S. Pat. No. 6,028,508 B1 deals with the problem of the onset of tread rubber separations. Here a sensor in the form of a laser is proposed, which sensor is aligned with the tread rubber of a tire. Curvatures or blisters that occur on the tread rubber are detected by the laser by a change in the distance between the tread rubber and the laser. However, such an arrangement is relatively complicated and expensive, since a laser source has to be assigned to each wheel, e.g., inside the wheel case. Accumulations of dirt and foreign bodies between the tread bars can also lead to misinterpretations.